// set content expiration 30 days in the futureheader('Expires: '. gmdate($http_date_format,mktime(0,0,0,gmdate('m',$gm_date),gmdate('d',$gm_date)+30,gmdate('Y',$gm_date)))); // set content last modified on the first of last monthheader('Last-Modified: '. gmdate($http_date_format,mktime(0,0,0,gmdate('m',$gm_date)-1,1,gmdate('Y',$gm_date)))); // HTTP/1.1header('Cache-Control: public');